Ghrelin and GHRP-6 enhance electrical and secretory activity in GC somatotropes

It is well established that pituitary somatotropes fire spontaneous action potentials (SAP) which generate Ca 2+ signals of sufficient amplitude to trigger growth hormone (GH) release. It is also known that ghrelin and synthetic GH-releasing peptides (GHRPs) stimulate GH secretion, though the mechan...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 2007-06, Vol.358 (1), p.59-65
Main Authors: Dominguez, Belisario, Felix, Ricardo, Monjaraz, Eduardo
Format: Article
Language:English
Subjects:
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester - pharmacology
Action Potentials - drug effects
Animals
Ca 2+ channels
Calcium Channel Agonists - pharmacology
Calcium Channel Blockers - pharmacology
Cell Line
Cell Line, Tumor
GC cells
Ghrelin
GHRP6
Growth hormone
Growth Hormone - secretion
Ion Channel Gating
Na + channels
Nifedipine - pharmacology
Oligopeptides - pharmacology
Patch clamp
Patch-Clamp Techniques
Peptide Hormones - pharmacology
Pituitary
Pituitary Neoplasms
Rats
Receptors, Somatotropin - metabolism
Somatotropes
Somatotrophs - drug effects
Somatotrophs - physiology
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Summary:It is well established that pituitary somatotropes fire spontaneous action potentials (SAP) which generate Ca 2+ signals of sufficient amplitude to trigger growth hormone (GH) release. It is also known that ghrelin and synthetic GH-releasing peptides (GHRPs) stimulate GH secretion, though the mechanisms involved remain unclear. In the current report, we show that the chronic (96 h) treatment with ghrelin and GHRP-6 increases the firing frequency of SAP in the somatotrope GC cell line. This action is associated with a significant increase in whole-cell inward current density. In addition, long-term application of Na + or L-type Ca 2+ current antagonists decreases GHRP-6-induced release of GH, indicating that the ionic currents that give rise to SAP play important roles for hormone secretion in the GC cells. Together, our results suggest that ghrelin and GHPR-6 may increase whole-cell inward current density thereby enhancing SAP firing frequency and facilitating GH secretion from GC somatotropes.
ISSN:0006-291X
1090-2104
DOI:10.1016/j.bbrc.2007.04.085